Lock-in Amplifier Circuit Design and Weak Signal Detection
Tian Zheng-w · Huagong zidonghua ji yibiao · 2014
The method of detecting weak signal and designing lock-in amplifier circuit was proposed,in which,having weak signal frequency obtained through analog PLL technology and the controller employed to detect phase-locked loop's output frequency so that a reference signal for relevant detection can be obtained according to the same frequency produced by the frequency value-based direct digital synthesis circuit. The system employs multiplier and integrator to accomplish the relevant detection,and through adjusting the reference signal step by step,the cross-correlation value can be maximized and the regeneration signal same as the measured signal in both frequency and phase can be obtained to implement detection and amplification of the weak signal,including both frequency and amplitude detection of the weak signal. The experimental tests show that this method has a high linearity at low SNR conditions and can be applied to the auto-detection and regenerative amplification of the arbitrary waveform's weak signal.